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1
CIVIL ENGINEERING
LAB MANUAL
Soil Mechanics
2
LIST OF EXPERIMENTS
Sl. No. Name of the Experiment Page No.
1. Determination of moisture content of the given soil sample. 3
2. Determination of specific gravity of the given soil sample. 5
3 Determine the in situ density of natural or compacted soils using sand
pouring cylinders.
8
4 Grain size analysis of soils using sieve analysis and using hydrometer
analysis test.
12
5 Determination of Consistency Limits 20
6 To determine the relative density of given coarse grained
Material.
29
7 To determine the coefficient of permeability of a soil using constant head
method. 33
8 To determine the moist density and dry density of soil sample using Proctor
Compaction Test.
45
9 To find shear strength of a given soil specimen Using Vane Shear
Apparatus.
50
10 To determine the shearing strength of the soil using the direct shear
apparatus.
53
11. Determine Shear Parameters of Cohesive Soil using unconfined
compression apparatus.
59
12 To find the shear of the soil by Undrained Triaxial Test.
64
13 To determine the settlements due to primary consolidation of soil by
conducting one dimensional test. 70
14 To determine the C.B.R value of given soil sample. 78
3
EXPERIMENT NO. 01
DETERMINATION OF MOISTURE CONTENT
OBJECTIVE
Determine the natural content of the given soil sample.
NEED AND SCOPE OF THE EXPERIMENT
In almost all soil tests natural moisture content of the soil is to be determined. The knowledge of
the natural moisture content is essential in all studies of soil mechanics. To sight a few, natural
moisture content is used in determining the bearing capacity and settlement. The natural moisture
content will give an idea of the state of soil in the field.
DEFINITION
The natural water content also called the natural moisture content is the ratio of the weight of
water to the weight of the solids in a given mass of soil. This ratio is usually expressed as
percentage.
APPARATUS REQUIRED
1. Non-corrodible air-tight container.
2. Electric oven, maintain the temperature between 1050 C to 1100 C.
3. Desiccator.
4. Balance of sufficient sensitivity.
PROCEDURE
1. Clean the container with lid, dry it and weigh it (W1).
2. Take a specimen of the sample in the container and weigh with lid (W2).
3. Keep the container in the oven with lid removed. Dry the specimen to constant weight
maintaining the temperature between 1050 C to 110
0 C for a period varying with the type of soil
but usually 16 to24 hours.
4
4. Record the final constant weight (W3) of the container with dried soil sample. Peat and other
organic soils are to be dried at lower temperature (say 600) possibly for a longer period.
Certain soils contain gypsum which on heating loses its water if crystallization. If it is suspected
that gypsum is present in the soil sample used for moisture content determination it shall be dried
at not more than 800
C and possibly for a longer time.
OBSERVATIONS AND RECORDING
Data and observation sheet for water content determination
Sl.No. Sample No. 1 2 3
1 Weight of container with lid W1
gm
2 Weight of container with lid +wet
soil W2 gm
3 Weight of container with lid +dry
soil W3 gm
4 Water/Moisture content
W = [(W2W3)/(W3W1)]100
INTERPRETATION AND REPORTING
RESULT
The natural moisture content of the soil sample is ________
GENERAL REMARKS
1. A container without lid can be used, when moist sample is weighed immediately after placing
the container and oven dried sample is weighed immediately after cooling in desiccators.
2. As dry soil absorbs moisture from wet soil, dried samples should be removed before placing
wet samples in the oven.
5
EXPERIMENT NO. 02
DETERMINATION OF SPECIFIC GRAVITY
OBJECTIVE
Determine the specific gravity of soil fraction passing 4.75 mm I.S sieve by density bottle.
NEED AND SCOPE
The knowledge of specific gravity is needed in calculation of soil properties like void ratio,
degree of saturation etc.
DEFINITION
Specific gravity G is defined as the ratio of the weight of an equal volume of distilled water at
that temperature both weights taken in air.
APPARATUS REQUIRED
1. Density bottle of 50 ml with stopper having capillary hole.
2. Balance to weigh the materials (accuracy 10gm).
3. Wash bottle with distilled water.
4. Alcohol and ether.
PROCEDURE
1. Clean and dry the density bottle
a. Wash the bottle with water and allow it to drain.
b. Wash it with alcohol and drain it to remove water.
c. Wash it with ether, to remove alcohol and drain ether.
2. Weigh the empty bottle with stopper (W1)
3. Take about 10 to 20 gm of oven soil sample which is cooled in desiccators. Transfer it to the
bottle. Find the weight of the bottle and soil (W2).
4. Put 10ml of distilled water in the bottle to allow the soil to soak completely. Leave it for about
2 hours.
5. Again fill the bottle completely with distilled water put the stopper and keep the bottle
6
Under constant temperature water baths (Tx0 ).
6. Take the bottle outside and wipe it clean and dry note. Now determine the weight of the bottle
and the contents (W3).
7. Now empty the bottle and thoroughly clean it. Fill the bottle with only distilled water and
weigh it. Let it be W4 at temperature (Tx0 C).
8. Repeat the same process for 2 to 3 times, to take the average reading of it.
OBSERVATIONS
S. No. Observation Number 1 2 3
1
2
3
4
Weight of density bottle (W1 g)
Weight of density bottle + dry soil
(W2 g)
Weight of bottle + dry soil + water
at temperature T x0
C (W3 g)
Weight of bottle + water (W4 g) at
temperature Tx0 C
Specific gravity G at Tx0 C
Average specific gravity at Tx0 C
CALCULATIONS
7
INTERPRETATION AND REPORTING
Unless or otherwise specified specific gravity values reported shall be based on water at 270C.
So the specific gravity at 270C = KSp. gravity at Tx
0C.
The specific gravity of the soil particles lie with in the range of 2.65 to 2.85. Soils containing
organic matter and porous particles may have specific gravity values below 2.0. Soils having
heavy substances may have values above 3.0
8
EXPERIMENT NO. 03
FIELD DENSITY TEST
SAND REPLACEMENT METHOD
OBJECTIVE
Determine the in situ density of natural or compacted soils using sand pouring cylinders.
NEED AND SCOPE
The in situ density of natural soil is needed for the determination of bearing capacity of soils, for
the purpose of stability analysis of slopes, for the determination of pressures on underlying strata
for the calculation of settlement and the design of underground structures.
It is very quality control test, where compaction is required, in the cases like embankment and
pavement construction.
APPARATUS REQUIRED
1. Sand pouring cylinder of 3 litre/16.5 litre capacity mounted above a pouring come and
separated by a shutter cover plate.
2. Tools for excavating holes; suitable tools such as scraper tool to make a level surface.
3. Cylindrical calibrating container with an internal diameter of 100 mm/200 mm and an internal
depth of 150 mm/250 mm fitted with a flange 50 mm/75 mm wide and about 5 mm surrounding
the open end.
4. Balance to weigh unto an accuracy of 1g.
5. Metal containers to collect excavated soil.
6. Metal tray with 300 mm/450 mm square and 40 mm/50 mm deep with a 100 mm/200 mm
diameter hole in the centre.
7. Glass plate about 450 mm/600 mm square and 10mm thick.
8. Clean, uniformly graded natural sand passing through 1.00 mm I.S. sieve and retained on the
600micron I.S .sieve. It shall be free from organic matter and shall have been oven dried and
exposed to atmospheric humidity.
9. Suitable non-corrodible airtight containers.
9
10. Thermostatically controlled oven with interior on non-corroding material to maintain the
temperature between 1050C to 110
0C.
11. A desiccator with any desiccating agent other than sulphuric acid.
THEORY
By conducting this test it is possible to determine the field density of the soil. The moisture
content is likely to vary from time and hence the field density also. So it is required to report the
test result in terms of dry density. The relationship that can be established between the dry
density with known moisture content is as follows:
PROCEDURE
Calibration of the Cylinder
1. Fill the sand pouring cylinder with clean sand so that the level of the sand in the cylinder is
within about 10 mm from the top. Find out the initial weight of the cylinder plus sand (W1) and
this weight should be maintained constant throughout the test for which the calibration is used.
2. Allow the sand of volume equal to that of the calibrating container to run out of the cylinder
by opening the shutter, close the shutter and place the cylinder on the glass sand takes place in
the cylinder close the shutter and remove the cylinder carefully. Weigh the sand collected on the
glass plate. Its weight (W2) gives the weight of sand filling the cone portion of the sand pouring
cylinder.
Repeat this step at least three times and take the mean weight (W2) Put the sand back into the
sand pouring cylinder to have the same initial constant weight (W1)
Determination of Bulk Density of Soil
3. Determine the volume (V) of the container be filling it with water to the brim. Check this
volume by calculating from the measured internal dimensions of the container.
4. Place the sand poring cylinder centrally on the of the calibrating container making sure that
constant weight (W1) is maintained. Open the shutter and permit the sand to run into the
10
container. When no further movement of sand is seen close the shutter, remove the pouring
cylinder and find its weight (W3).
Determination of Dry Density of Soil in Place
5. Approximately 60 sq.cm of area of soil to be tested should be trimmed down to a level
surface, approximately of the size of the container. Keep the metal tray on the level surface and
excavate a circular hole of volume equal to that of the calibrating container. Collect all the
excavated soil in the tray and find out the weight of the excavated soil (Ww). Remove the tray,
and place the sand pouring cylinder filled to constant weight so that the base of the cylinder
covers the hole concentrically. Open the shutter and permit the sand to run into the hole. Close
the shutter when no further movement of the sand is seen. Remove the cylinder and determine its
weight (W3).
6. Keep a representative sample of the excavated sample of the soil for water content
determination.
OBSERVATIONS AND CALCULATIONS
S. No.
Sample Details
Calibration
1 2 3
1.
2.
3.
4.
5.
6.
Weight of sand in cone (of pouring cylinder)
W2 gm
Volume of calibrating container (V) in cc
Weight of sand + cylinder before pouring W3
gm
Weight of sand + cylinder after pouring W3 gm
Weight of sand to fill calibrating containers
Wa = (W1-W3-W2) gm
Bulk density of sand s = Wa / V gm/cc
11
GENERAL REMARKS
1. While calibrating the bulk density of sand great care has to be taken.
2. The excavated hole must be equal to the volume of the calibrating container.
S. No. Measurement of Soil Density 1 2 3
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Weight of wet soil from hole Ww gm
Weight of sand + cylinder before pouring W1
gm
Weight of sand + cylinder after pouring W4
gm
Weight of sand in hole Wb = (W1-W2-W4)
gm
Bulk density b = (Ww /Wb) s gm/cc
Water content determination
Container number
Weight of wet soil
Weight of dry soil
Moisture content (%)
Dry density d = b / (1+w) gm/cc
12
EXPERIMENT NO. 04
GRAIN SIZE DISTRIBUTION
I.SIEVE ANALYSIS
OBJECTIVE
(a). Select sieves as per I.S specifications and perform sieving.
(b). Obtain percentage of soil retained on each sieve.
(c). Draw graph between log grain size of soil and % finer.
NEED AND SCOPE OF EXPERIMEN
The grain size analysis is widely used in classification of soils. The data obtained from grain size
distribution curves is used in the design of filters for earth dams and to determine suitability of
soil for road construction, air field etc. Information obtained from grain size analysis can be used
to predict soil water movement although permeability tests are more generally used.
PLANNING AND ORGANISATION
Apparatus
1. Balance
2. I.S sieves
3. Rubber pestle and mortar.
4. Mechanical Sieve Shaker
The grain size analysis is an attempt to determine the relative proportions of different grain sizes
which make up a given soil mass.
13
KNOWLEDGE OF EQUIPMENT
1. The balance to be used must be sensitive to the extent of 0.1% of total weight of sample taken.
2. I.S 460-1962 is to used. The sieves for soil tests: 4.75 mm to 75 microns.
PROCEDURE
1. For soil samples of soil retained on 75 micron I.S sieve
(a) The proportion of soil sample retained on 75 micron I.S sieve is weighed and recorded
weight of soil sample is as per I.S 2720.
(b) I.S sieves are selected and arranged in the order as shown in the table.
(c) The soil sample is separated into various fractions by sieving through above sieves
placed in the above mentioned order.
(d) The weight of soil retained on each sieve is recorded.
(e) The moisture content of soil if above 5% it is to be measured and recorded.
2. No particle of soil sample shall be pushed through the sieves.
14
OBSERVATIONS AND RECORDING
Weight of soil sample:…..
Moisture content:……..
I.S sieve
number or
size in mm
Wt. Retained
in each sieve
(gm)
Percentage
on each sieve
Cumulative
%age
retained on
each sieve
% finer Remarks
4.75
4.00
3.36
2.40
1.46
1.20
0.60
0.30
0.15
0.075
GRAPH
15
Draw graph between log sieve size vs % finer. The graph is known as grading curve.
Corresponding to 10%, 30% and 60% finer, obtain diameters from graph are designated as D10,
D30, D60.
CALCULATION
1. The percentage of soil retained on each sieve shall be calculated on the basis of total
weight of soil sample taken.
2. Cumulative percentage of soil retained on successive sieve is found.
II.HYDROMETER ANALYSIS
OBJECTIVE
Grain size analysis of soils by hydrometer analysis test.
SPECIFIC OBJECTIVE
1. To determine the grain size distribution of soil sample containing appreciable amount of fines.
2. To draw a grain size distribution curve.
NEED AND SCOPE OF THE EXPERIMENT
For determining the grain size distribution of soil sample, usually mechanical analysis (sieve
analysis) is carried out in which the finer sieve used is 63 micron or the nearer opening. If a soil
contains appreciable quantities of fine fractions in (less than 63 micron) wet analysis is done.
One form of the analysis is hydrometer analysis. It is very much helpful to classify the soil as per
ISI classification. The properties of the soil are very much influenced by the amount of clay and
other fractions.
16
APPARATUS
1. Hydrometer
2. Glass measuring cylinder-Two of 1000 ml capacity with ground glass or rubber stoppers
about 7 cm diameter and 33 cm high marked at 1000 ml volume.
3. Thermometer- To cover the range 0 to 50o C with an accuracy of 0.5
o C .
4. Water bath.
5. Stirring apparatus.
6. I.S sieves apparatus.
7. Balance-accurate to 0.01 gm.
8. Oven-105 to 110.
9. Stop watch.
10. Desiccators
11. Centimeter scale.
12. Porcelain evaporating dish.
13. Wide mouth conical flask or conical beaker of 1000 ml capacity.
14. Thick funnel-about 10 cm in diameter.
15. Filter flask-to take the funnel.
16. Measuring cylinder-100 ml capacity.
17. Wash bottle-containing distilled water.
18. Filter papers.
19. Glass rod-about 15 to 20 cm long and 4 to 5 mm in diameter.
20. Hydrogen peroxide-20 volume solution.
21. Hydrochloric acid N solution-89 ml of concentrated hydrochloric acid.(specific gravity
1.18) diluted with distilled water one litre of solution.
22. Sodium hexa meta phosphate solution-dissolve 33 g of sodium hexa meta phosphate and
7 gms of sodium carbonate in distilled water to make one litre of solution.
17
CALIBRATION OF HYDROMETER
Volume
(a) Volume of water displaced: Approximately 800 ml of water shall be poured in the 1000 ml
measuring cylinder. The reading of the water level shall be observed and recorded.
The hydrometer shall be immersed in the water and the level shall again be observed and
recorded as the volume of the hydrometer bulb in ml plus volume of that part of the stem that is
submerged. For practical purposes the error to the inclusion of this stem volume may be
neglected.
(b) From the weight of the hydrometer: The hydrometer shall be weighed to the nearest 0.1 gm.
The weight in gm shall be recorded as the volume of the bulb plus the volume of the stem below
the 1000 ml graduation mark. For practical purposes the error due to the inclusion of this stem
may be neglected.
Calibration
(a) The sectional area of the 1000 ml measuring cylinder in which the hydrometer is to used shall
be determined by measuring the distance between the graduations. The sectional area is equal to
the volume include between the two graduations divided by the measured distance between
them. Place the hydrometer on the paper and sketch it. On the sketch note the lowest and highest
readings which are on the hydrometer and also mark the neck of the bulb. Mark the center of the
bulb which is half of the distance between neck of the bulb and tip of the bulb.
(b) The distance from the lowest reading to the center of the bulb is (Rh) shall be recorded
(Rh =HL + L/2).
(c) The distance from the highest hydrometer reading to the center of the bulb shall be measured
and recorded.
18
(d) Draw a graph hydrometer readings vs HH and RH. A straight line is obtained. This calibration
curve is used to calibrate the hydrometer readings which are taken with in 2 minutes.
(e) From 4 minutes onwards the readings are to be taken by immersing the hydrometer each
time. This makes the soil solution to rise, there by rising distance of free fall of the particle. So
correction is applied to the hydrometer readings.
(f) Correction applied to the Rh and HH
Vh= Volume of hydrometer bulb in ml.
A =Area of measuring cylinder in cm2.
From these two corrected readings draw graph (straight line)
Grain Size Distribution in Soil-Data and Calculation Chart
Date:……….
Sample No:
Total weight of dry soil taken, W =
Specific Gravity of soil, G =
Hydrometer No………. Wt. Of soil gone into solution ,Ws =
Meniscus correction, Cn = Dispersion agent correction(Cd) =
19
Reading in water RW =
Temperature correction(Ct) =
% finer for wt. of soil Ws gone into solution N=[(100G)/{Ws x (G- 1)}] x R
Date Time
Elapsed
Time in
Sec
Hydrometer
reading
upper
Meniscus
Rh -1000
Corrected
hydrometer
Reading
(lower
meniscus
Cm)
Zr
or
Zlr
Velocity
cms/sec
V=Zr/K
or Zr1
/ t
Equivalent
dia. of
Particle
Dmm
R
N(%
finer
than
for
soil)
REMARKS
20
EXPERIMENT NO. 05
DETERMINATION OF CONSISTENCY LIMITS
I.LIQUID LIMIT TEST
OBJECTIVE
1. Prepare soil specimen as per specification.
2. Find the relationship between water content and number of blows.
3. Draw flow curve.
4. Find out liquid limit.
NEED AND SCOPE
Liquid limit is significant to know the stress history and general properties of the soil met with
construction. From the results of liquid limit the compression index may be estimated. The compression
index value will help us in settlement analysis. If the natural moisture content of soil is closer to liquid
limit, the soil can be considered as soft if the moisture content is lesser than liquids limit, the soil can be
considered as soft if the moisture content is lesser than liquid limit. The soil is brittle and stiffer.
THEORY
The liquid limit is the moisture content at which the groove, formed by a standard tool into the sample of
soil taken in the standard cup, closes for 10 mm on being given 25 blows in a standard manner. At this
limit the soil possess low shear strength.
APPARATUS REQUIRED
1. Balance 2. Liquid limit device (Casagrende’s) 3. Grooving tool 4. Mixing dishes
5. Spatula 6. Electrical Oven
PROCEDURE
1. About 120 gm of air-dried soil from thoroughly mixed portion of material passing 425 micron I.S
sieve is to be obtained.
21
2. Distilled water is mixed to the soil thus obtained in a mixing disc to form uniform paste. The paste
shall have a consistency that would require 30 to 35 drops of cup to cause closer of standard groove for
sufficient length.
3. A portion of the paste is placed in the cup of LIQUID LIMIT device and spread into portion with few
strokes of spatula.
4. Trim it to a depth of 1cm at the point of maximum thickness and return excess of soil to the dish.
5. The soil in the cup shall be divided by the firm strokes of the grooving tool along the diameter through
the centre line of the follower so that clean sharp groove of proper dimension is formed.
6. Lift and drop the cup by turning crank at the rate of two revolutions per second until the two halves of
soil cake come in contact with each other for a length of about 1 cm by flow only.
7. The number of blows required to cause the groove close for about 1 cm shall be recorded.
8. A representative portion of soil is taken from the cup for water content determination.
9. Repeat the test with different moisture contents at least three more times for blows between 10 and 40.
22
OBSERVATIONS
Details of the sample:.......
Natural moisture content:........ Room temperature:..............
Determination Number 1 2 3 4
Container number
Weight of container
Weight of container + wet soil
Weight of container + dry soil
Weight of water
Weight of dry soil
Moisture content (%)
No. of blows
COMPUTATION / CALCULATION
Draw a graph showing the relationship between water content (on y-axis) and number of blows (on x-
axis) on semi-log graph. The curve obtained is called flow curve. The moisture content corresponding to
25 drops (blows) as read from the represents liquid limit. It is usually expressed to the nearest whole
number.
INTERPRETATION AND RECORDING
Flow index If = (W2-W1)/(logN1/N2) = slope of the flow curve.
Plasticity Index = wL-wp =
Toughness Index = Ip/If =
23
II.PLASTIC LIMIT TEST
NEED AND SCOPE
Soil is used for making bricks, tiles , soil cement blocks in addition to its use as foundation for structures.
APPARATUS REQUIRED
1. Porcelain dish.
2. Glass plate for rolling the specimen.
3. Air tight containers to determine the moisture content.
4. Balance of capacity 200gm and sensitive to 0.01gm
5.Oven thermostatically controlled with interior of non-corroding material to maintain the
temperature around 1050 and 110
0C.
PROCEDURE
1. Take about 20gm of thoroughly mixed portion of the material passing through 425 micron I.S. sieve
obtained in accordance with I.S. 2720 (part 1).
2. Mix it thoroughly with distilled water in the evaporating dish till the soil mass becomes plastic
enough to be easily molded with fingers.
3. Allow it to season for sufficient time (for 24 hrs) to allow water to permeate throughout the
soil mass
4. Take about 10gms of this plastic soil mass and roll it between fingers and glass plate with just
sufficient pressure to roll the mass into a threaded of uniform diameter throughout its length.
The rate of rolling shall be between 60 and 90 strokes per minute.
5. Continue rolling till you get a threaded of 3 mm diameter.
6. Kneed the soil together to a uniform mass and re-roll.
7. Continue the process until the thread crumbles when the diameter is 3 mm.
8. Collect the pieces of the crumbled thread in air tight container for moisture content
determination.
24
9. Repeat the test to at least 3 times and take the average of the results calculated to the nearest
whole number.
OBSERVATION AND REPORTING
Compare the diameter of thread at intervals with the rod. When the diameter reduces to 3 mm,
note the surface of the thread for cracks.
PRESENTATION OF DATA
Container No.
Wt. of container + lid,W1
Wt. of container + lid + wet sample,W2
Wt. of container + lid + dry sample,W3
Wt. of dry sample = W3 − W1
Wt. of water in the soil = W3− W2
Water content (%) = (W3 −W2) / (W3 − W1)
×100
Average Plastic Limit=...............
25
III.SHRINKAGE LIMIT TEST
OBJECTIVE
To determine the shrinkage limit and calculate the shrinkage ratio for the given soil.
THEORY
As the soil loses moisture, either in its natural environment, or by artificial means in laboratory it
changes from liquid state to plastic state, from plastic state to semi-solid state and then to solid
state. Volume changes also occur with changes in water content. But there is particular limit at
which any moisture change does not cause soil any volume change.
NEED AND SCOPE
Soils which undergo large volume changes with change in water content may be troublesome.
Volume changes may not and usually will not be equal.
A shrinkage limit test should be performed on a soil.
1. To obtain a quantitative indication of how much change in moisture can occur before any
appreciable volume changes occurs
2. To obtain an indication of change in volume.
The shrinkage limit is useful in areas where soils undergo large volume changes when going
through wet and dry cycles (as in case of earth dams)
APPARATUS
1. Evaporating Dish.
2. Spatula
3. Shrinkage Dish. Circular, porcelain or non-corroding metal dish (3 nos.) having a flat
bottom and 45 mm in diameter and 15 mm in height internally.
4. Straight Edge Steel, 15 cm in length.
5. Glass cup. 50 to 55 mm in diameter and 25 mm in height, the top rim of which is ground
smooth and level.
26
6. Glass plates. Two, each 75 75 mm one plate shall be of plain glass and the other shall have
prongs.
7. Sieves. 2mm and 425- micron IS sieves.
8. Oven-thermostatically controlled.
9. Graduate-Glass, having a capacity of 25 ml and graduated to 0.2 ml and 100 cc one mark
flask.
10. Balance-Sensitive to 0.01 g minimum.
11. Mercury. Clean, sufficient to fill the glass cup to over flowing.
12. Wash bottle containing distilled water.
PROCEDURE
Preparation of soil paste
1. Take about 100 gm of soil sample from a thoroughly mixed portion of the material passing
through 425-micron I.S. sieve.
2. Place about 30 gm the above soil sample in the evaporating dish and thoroughly mixed with
distilled water and make a creamy paste. Use water content somewhere around the liquid limit.
Filling the shrinkage dish
3. Coat the inside of the shrinkage dish with a thin layer of Vaseline to prevent the soil sticking
to the dish.
4. Fill the dish in three layers by placing approximately 1/3 rd of the amount of wet soil with the
help of spatula. Tap the dish gently on a firm base until the soil flows over the edges and no
apparent air bubbles exist. Repeat this process for 2nd and 3rd layers also till the dish is
completely filled with the wet soil. Strike off the excess soil and make the top of the dish
smooth. Wipe off all the soil adhering to the outside of the dish.
5. Weigh immediately, the dish with wet soil and record the weight.
6. Air- dry the wet soil cake for 6 to 8hrs, until the colour of the pat turns from dark to light.
Then oven-dry the constant temp. at 1050C to 110
0C say about 12 to 16 hrs.
27
7. Remove the dried disk of the soil from oven. Cool it in a desicator. Then obtain the weight of
the dish with dry sample.
8. Determine the weight of the empty dish and record.
9. Determine the volume of shrinkage dish which is evidently equal to volume of the wet soil as
follows. Place the shrinkage dish in an evaporating dish and fill the dish with mercury till it
overflows slightly. Press it with plain glass plate firmly on its top to remove excess mercury.
Pour the mercury from the shrinkage dish into a measuring jar and find the volume of the
shrinkage dish directly. Record this volume as the volume of the wet soil pat.
Volume of the Dry Soil Pat
10. Determine the volume of dry soil pat by removing the pat from the shrinkage dish and
immersing it in the glass cup full of mercury in the following manner.
Place the glass cup in a larger one and fill the glass cup to overflowing with mercury. Remove
the excess mercury by covering the cup with glass plate with prongs and pressing it. See that no
air bubbles are entrapped. Wipe out the outside of the glass cup to remove the adhering mercury.
Then, place it in another larger dish, which is, clean and empty carefully.
Place the dry soil pat on the mercury. It floats submerge it with the pronged glass plate which is
again made flush with top of the cup. The mercury spills over into the larger plate. Pour the
mercury that is displayed by the soil pat into the measuring jar and find the volume of the soil pat
directly.
CALCULATION
CAUTION
Do not touch the mercury with gold rings.
28
TABULATION AND RESULTS
S.No Determination No. 1 2 3
Wt. of container in gm,W1
Wt. of container + wet soil pat in gm,W2
Wt. of container + dry soil pat in gm,W3
Wt. of oven dry soil pat, W0 in gm
Wt. of water in gm
Moisture content (%), W
Volume of wet soil pat (V), in cm
Volume of dry soil pat (V0) in cm3
By mercury displacement method
a. Weight of displaced mercury
b. Specific gravity of the mercury
Shrinkage limit (WS)
Shrinkage ratio (R)
29
EXPERIMENT NO. 06
RELATIVE DENSITY TEST
OBJECTIVE
To determine the relative density of given coarse grained material.
PLANNING AND ORGANISATION
Cushioned steel vibrating deck 7575 cm size, R.P.M: 3600; under a 115 kg load, 440V, 3 phase
supply.
Two cylindrical metallic moulds, 3000 cc and 15000 cc.
10 mm thick surcharge base plate with handle separately for each mould. Surcharge weights, one
for each size having a weight equal to 140 gms / sq.cm.
Dial gauge holder, which can be slipped into the eyelets on the moulds sides.
Guide sleeves with clamps for each mould separately.
Calibration bar 753003 mm.
DEFINITIONS
Relative density or density index is the ratio of the difference between the void ratios of a
cohesionless soil in its loosest state and existing natural state to the difference between its void
ratio in the loosest and densest states.
Where,
emax = void ratio of coarse grained soil ( cohesionless) in its loosest state.
emin = void ratio of coarse grained soil ( cohesionless) in its densest state.
30
e = void ratio of coarse grained soil (cohesionless) in its natural existing state in the field.
THEORY
Porosity of a soil depends on the shape of grain, uniformity of grain size and condition of
sedimentation. Hence porosity itself does not indicate whether a soil is in loose or dense state.
This information can only be obtained by comparing the porosity or void ratio of the given soil
with that of the same soil in its loosest and densest possible state and hence the term, relative
density is introduced.
Relative density is an arbitrary character of sandy deposit. In real sense, relative density
expresses the ratio of actual decrease in volume of voids in a sandy soil to the maximum possible
decrease in the volume of voids i.e how far the sand under investigation can be capable to the
further densification beyond its natural state. Determination of relative density is helpful in
compaction of coarse grained soils and in evaluating safe bearing capacity in case of sandy soils.
For very dense gravelly sand, it is possible to obtain relative density greater the one. This means
that such natural dense packing could not be obtained in the laboratory.
31
PROCEDURE
Calibration of mould:
1. Measure inside diameter of mould at different depths using a bore gauge and take the average.
2. Keep the mould on a flat surface or flat plate. Measure the height at different positions and
take the average (accuracy = 0.025 mm).
3. Calculate the volume.
4. Fill the mould with distilled water till over flowing takes place.
5. Slid thick glass plate over the top surface of mould.
6. Weigh the water filling the mould.
7. Note the temperature of water.
8. Obtain density of water for the above temperature from physical tables.
9. Calculate the volume of the mould which is weight of water filling the mould /density of
water.
Preparation of the Sample:
1. Dry the soil sample in a thermostatically controlled electric oven.
2. Cool in the sample in a desicator.
3. Segregate soil lumps without breaking individual particles
4. Sieve it through the required sieve size.
Minimum Density:
The mould is weighed accurately (W). Pour the dry pulverized soil into the mould through a
funnel in a steady stream. The spout is adjusted so that the free fall of soil particle is always 25
mm. While pouring soil the spout must have a spiral motion from the rim to the centre. The
32
process is continued to fill up the mould with soil up to about 25mm above the top. It is then
leveled, with the soil and weight is recorded (W1).
Maximum Density:
Weigh the empty mould (W). Put the collar on top of the mould and clamp it. Fill the mould with
the oven dried soil sample till 1 / 2 or 2 / 3 of the collar is filled. Place the mould on the vibrating
deck and fix it with nuts and bolts. Then place the surcharge weight on it. The vibrator is allowed
to run for 8 minutes. Then mould is weighed with the soil and weight is recorded (W2).
Natural Density:
Weigh the mould with dry soil. Knowing the volume of the mould and weight of dry soil natural
density, d, can be calculated.
33
EXPERIMENT NO. 07
PERMEABILITY TEST
A. CONSTANT HEAD
OBJECTIVE
To determine the coefficient of permeability of a soil using constant head method.
NEED AND SCOPE
The knowledge of this property is much useful in solving problems involving yield of water
bearing strata, seepage through earthen dams, stability of earthen dams, and embankments of
canal bank affected by seepage, settlement etc.
PLANNING AND ORGANIZATION
1. Preparation of the soil sample for the test
2. Finding the discharge through the specimen under a particular head of water.
DEFINITION OF COEFFICIENT OF PERMEABILITY
The rate of flow under laminar flow conditions through a unit cross sectional are of porous
medium under unit hydraulic gradient is defined as coefficient of permeability.
EQUIPMENT
1. Permeameter mould of non-corrodible material having a capacity of 1000 ml, with an internal
diameter of 100 0.1 mm and internal effective height of 127.3 0.1 mm.
2. The mould shall be fitted with a detachable base plate and removable extension counter.
3. Compacting equipment: 50 mm diameter circular face, weight 2.76 kg and height of fall 310
mm as specified in I.S 2720 part VII 1965.
34
4. Drainage bade: A bade with a porous disc, 12 mm thick which has the permeability 10 times
the expected permeability of soil.
5. Drainage cap: A porous disc of 12 mm thick having a fitting for connection to water inlet or
outlet.
6. Constant head tank: A suitable water reservoir capable of supplying water to the permeameter
under constant head.
7. Graduated glass cylinder to receive the discharge.
8. Stop watch to note the time.
9. A meter scale to measure the head differences and length of specimen.
PREPARATION OF SPECIMEN FOR TESTING
A. UNDISTURBED SOIL SAMPLE
1. Note down the sample number, bore hole number and its depth at which the sample was taken.
2. Remove the protective cover (paraffin wax) from the sampling tube.
3. Place the sampling tube in the sample extraction frame, and push the plunger to get a
cylindrical form sample not longer than 35 mm in diameter and having height equal to that of
mould.
4. The specimen shall be placed centrally over the porous disc to the drainage base.
5. The angular space shall be filled with an impervious material such as cement slurry or wax, to
provide sealing between the soil specimen and the mould against leakage from the sides.
6. The drainage cap shall then be fixed over the top of the mould.
7. Now the specimen is ready for the test.
35
DISTURBED SOIL SAMPLE
1. A 2.5 kg sample shall be taken from a thoroughly mixed air dried or oven dried material.
2. The initial moisture content of the 2.5 kg sample shall be determined. Then the soil shall be
placed in the air tight container.
3. Add required quantity of water to get the desired moisture content.
4. Mix the soil thoroughly.
5. Weigh the empty permeameter mould.
6. After greasing the inside slightly, clamp it between the compaction base plate and extension
collar.
7. Place the assembly on a solid base and fill it with sample and compact it.
8. After completion of a compaction the collar and excess soil are removed.
9. Find the weight of mould with sample.
10. Place the mould with sample in the permeameter, with drainage base and cap having discs
that are properly saturated.
TEST PROCEDURE
1. For the constant head arrangement, the specimen shall be connected through the top inlet to
the constant head reservoir.
2. Open the bottom outlet.
3. Establish steady flow of water.
4. The quantity of flow for a convenient time interval may be collected.
36
5. Repeat three times for the same interval.
OBSERVATION AND RECORDING
The flow is very low at the beginning, gradually increases and then stands constant. Constant
head permeability test is suitable for cohesionless soils. For cohesive soils falling head method is
suitable.
COMPUTATION
Coefficient of permeability for a constant head test is given by
Presentation of data
The coefficient of permeability is reported in cm/sec at 27o C. The dry density, the void ratio and
the degree of saturation shall be reported. The test results should be tabulated as below:
Permeability Test Record
Project:
Tested By:
Location:
Boring No.
37
Depth:
Details of sample
Diameter of specimen………..cm
Length of specimen (L)………...cm
Area of specimen (A) ………..cm2
Specific gravity of soil Gs …….
Volume of specimen (V)……..cm3
Weight of dry specimen (Ws) ……gm
Moisture content…….%
Experiment No.
1 2 3
Length of
specimen L(cm)
Area of
specimen A(cm
2)
Time t (sec)
Discharge q(cm3)
Height of water h(cm)
Temperature (o C)
38
Interpretation and Reporting
39
B. FALLING HEAD METHOD
OBJECTIVE
To determine the coefficient of permeability of the given soil sample, using falling head
method.
NEED AND SCOPE
The test results of the permeability experiments are used:
1. To estimate ground water flow.
2. To calculate seepage through dams.
3. To find out the rate of consolidation and settlement of structures.
4. To plan the method of lowering the ground water table.
5. To calculate the uplift pressure and piping.
6. To design the grouting.
7. And also for soil freezing tests.
8. To design pits for recharging.
Thus the study of seepage of water through soil is very important, with wide field
applications.
The falling head method of determining permeability is used for soil with low discharge,
where as the constant head permeability test is used for coarse-grained soils with a
reasonable discharge in a given time. For very fine-grained soil, capillarity permeability test
is recommended.
PRINCIPLE OF THE EXPERIMENT
The passage of water through porous material is called seepage. A material with continuous
voids is called a permeable material. Hence permeability is a property of a porous material
which permits passage of fluids through inters connecting conditions.
40
Hence permeability is defined as the rate of flow of water under laminar conditions
through a unit cross-sectional area perpendicular to the direction of flow through a porous
medium under unit hydraulic gradient and under standard temperature conditions.
The principle behind the test is Darcy’s law for laminar flow. The rate of discharge is
proportional to (i x A)
q= kiA
Where q= Discharge per unit time.
A=Total area of c/s of soil perpendicular to the direction of flow.
i=hydraulic gradient.
k=Darcy’s coefficient of permeability = the mean velocity of flow that will occur through the
cross-sectional area under unit hydraulic gradient.
PLANNING AND ORGANIZATION
The tools and accessories needed for the test are:
1. Permeameter with its accessories.
2. Standrd soil specimen.
3. Deaires water.
4. Balance to weigh up to 1 gm.
5. I.S sieves 4.75 mm and 2 mm.
6. Mixing pan.
7. Stop watch.
8. Measuring jar.
41
9. Meter scale.
10. Thermometer.
11. Container for water.
12. Trimming knife etc.
KNOWLEDGE OF EQUIPMENT
(a) The permeameter is made of non-corrodible material with a capacity of 1000 ml, with an
internal diameter of 1000.1 mm and effective height of 127.3 0.1 mm.
(b) The mould has a detachable base plate and a removable exterior collar.
(c) The compacting equipment has a circular face with 50 mm diameter and a length of 310
mm with a weight of 2.6 kg.
(d) The drainage base is a porous disc, 12 mm thick with a permeability 10 times that of soil.
(e) The drainage cap is also a porous disc of 12 mm thickness with an inlet/outlet fitting.
(f) The container tank has an overflow valve. There is also a graduated jar to collect
discharge.
(g) The stand pipe arrangements are done on a board with 2 or 3 glass pipes of different
diameters.
PREPARATION OF THE SPECIMEN
The preparation of the specimen for this test is important. There are two types of
specimen, the undisturbed soil sample and the disturbed or made up soil sample.
A. UNDISTURBED SOIL SPECIMEN
It is prepared as follows:
42
1. Note down-sample no., borehole no., depth at which sample is taken.
2. Remove the protective cover (wax) from the sampling tube.
3.Place the sampling tube in the sample extract or and push the plunger to get a cylindrical
shaped specimen not larger than 85 mm diameter and height equal to that of the mould.
4. This specimen is placed centrally over the drainage disc of base plate.
5. The annular space in between the mould and specimen is filled with an impervious material
like cement slurry to block the side leakage of the specimen.
6. Protect the porous disc when cement slurry is poured.
7. Compact the slurry with a small tamper.
8. The drainage cap is also fixed over the top of the mould.
9. The specimen is now ready for test.
B. DISTURBED SPECIMEN
The disturbed specimen can be prepared by static compaction or by dynamic compaction.
(a)Preparation of statically Compacted (disturbed) specimen.
1. Take 800 to 1000 gms of representative soil and mix with water to O.M.C determined by I.S
Light Compaction test. Then leave the mix for 24 hours in an airtight container.
2. Find weight (W) of soil mix for the given volume of the mould and hence find the dry .
3. Now, assemble the permeameter for static compaction. Attach the 3 cm collar to the bottom
end of 0.3 liters mould and the 2 cm collar to the top end. Support the mould assembly over 2.5
43
cm end plug, with 2.5 cm collar resting on the split collar kept around the 2.5 cm- end plug. The
inside of the 0.3 lit. Mould is lightly greased.
4. Put the weighed soil into the mould. Insert the top 3 cm end plug into the top collar, tamping
the soil with hand.
5. Keep, now the entire assembly on a compressive machine and remove the split collar. Apply
the compressive force till the flange of both end plugs touches the corresponding collars.
Maintain this load for 1 mt and then release it.
6. Then remove the top 3 cm plug and collar place a filter paper on fine wire mesh on the top of
the specimen and fix the perforated base plate.
7. Turn the mould assembly upside down and remove the 2.5 cm end plug and collar. Place the
top perforated plate on the top of the soil specimen and fix the top cap on it, after inserting the
seating gasket.
8. Now the specimen is ready for test.
(B) Preparation of Dynamically Compacted Disturbed sample:
1. Take 800 to 1000 gms of representative soil and mix it with water to get O.M.C, if necessary.
Have the mix in airtight container for 24 hours.
2. Assemble the permeameter for dynamic compaction. Grease the inside of the mould and place
it upside down on the dynamic compaction base. Weigh the assembly correct to a gram (w). Put
the 3 cm collar to the other end.
3. Now, compact the wet soil in 2 layers with 15 blows to each layer with a 2.5 kg dynamic tool.
Remove the collar and then trim off the excess. Weigh the mould assembly with the soil (W2).
4. Place the filter paper or fine wore mesh on the top of the soil specimen and fix the perforated
base plate on it.
44
5. Turn the assembly upside down and remove the compaction plate. Insert the sealing gasket
and place the top perforated plate on the top of soil specimen. And fix the top cap.
6. Now, the specimen is ready for test.
EXPERIMENTAL PROCEDURE
1. Prepare the soil specimen as specified.
2. Sturate it. Deaired water is preferred.
3. Assemble the permeameter in the bottom tank and fill the tank with water.
4. Inlet nozzle of the mould is connected to the stand pipe. Allow some water to flow until steady
flow is obtained.
5. Note down the time interval (t) for a fall of head in the stand pipe (h).
6. Repeat step 5 three times to determine (t) for the same head.
7. Find (a) by collecting (q) for the stand pipe. Weigh it correct to 1 gm and find (a) from q/h=a.
Therefore the coefficient of permeability
45
Observation and Recording:
1st set 2
nd set
1. Area of stand pipe (dia. 5 cm)= a=…..
2.Cross sectional area of soil specimen A
3.Length of soil specimen,L
4.Initial reading of stand pipe, h1
5.Final reading of stand pipe, h2
6.Time,t
7.Test temperature,T
8.Coefficientof permeability at T, kt
9.Coefficient of permeability at 27o C, k27
46
GENERAL REMARKS:
1. During test there should be no volume change in the soil, there should be no
compressible air present in the voids of soil i.e. soil should be completely saturated. The
flow should be laminar and in a steady state condition.
2. Coefficient of permeability is used to assess drainage characteristics of soil, to predict rate
of settlement founded on soil bed.
47
EXPERIMENT NO. 08
PROCTOR TEST
OBJECTIVE
To determine the moist density and dry density of soil sample using proctor compaction test.
SCOPE
This method covers the determination of the relationship between the moisture content and
density of soils compacted in a mould of a given size with a 2.5 kg rammer dropped from a
height of 30 cm.
APPARATUS
1. Proctor mould having a capacity of 944 cc with an internal diameter of 10.2 cm and a
height of 11.6 cm. The mould shall have a detachable collar assembly and a detachable
base plate.
2. Rammer: A mechanical operated metal rammer having a 5.08 cm diameter face and a
weight of 2.5 kg. The rammer shall be equipped with a suitable arrangement to control
the height of drop to a free fall of 30 cm.
3. Sample extruder.
4. A balance of 15 kg capacity.
5. Sensitive balance.
6. Straight edge.
7. Graduated cylinder.
8. Mixing tools such as mixing pan, spoon, towel, spatula etc.
9. Moisture tins.
PROCEDURE
Take a representative oven-dried sample, approximately 5 kg in the given pan.
Thoroughly mix the sample with sufficient water to dampen it to approximately four to six
percentage points below optimum moisture content.
48
Weigh the proctor mould without base plate and collar. Fix the collar and base plate. Place the
soil in the Proctor mould and compact it in 3 layers giving 25 blows per layer with the 2.5 kg
rammer falling through.
Remove the collar, trim the compacted soil even with the top of the mould by means of
the straight edge and weigh.
Divide the weight of the compacted specimen by 944 cc and record the result as the wet
weight wet in grams per cubic centimeter of the compacted soil.
Remove the sample from the mould and slice vertically through and obtain a small
sample for moisture determination.
Thoroughly break up the remainder of the material until it will pass a no.4 sieve as
judged by the eye. Add water in sufficient amounts to increase the moisture content of the soil
sample by one or two percentage points and repeat the above procedure for each increment of
water added. Continue this series of determination until there is either a decrease or no change in
the wet unit weight of the compacted soil.
CALCULATION
Wet density gm/cc =weight of compacted soil / 944.
Dry density = wet density/(1+w)
Where w is the moisture content of the soil.
Plot the dry density against moisture content and find out the maximum dry density and optimum
moisture for the soil.
49
OBSERVATIONS
Cylinder diameter……………. cm.
a. height ……………………… cm
b. volume ……………………..cc
Weight of cylinder ……………gm
Density
Determination No.
Water to be added (percent)
Weight of water to be added (gm)
Weight of cylinder + compacted soil
Weight of compacted soil (gms)
Average moisture content (percent)
Wet density
(gm /cc)
Dry density (gm/cc)
Water content
Container No.
Wt. Of container + wet soil gms.
Wt. Of container + dry soil, gms
Wt of container alone gms.
Wt. Of water gm
Wt. Of dry soil gms.
Percentage of water
Content
50
EXPERIMENT NO. 09
VANE SHEAR TEST
OBJECTIVE
To find shear strength of a given soil specimen.
NEED AND SCOPE
The structural strength of soil is basically a problem of shear strength.
Vane shear test is a useful method of measuring the shear strength of clay. It is a cheaper and
quicker method. The test can also be conducted in the laboratory. The laboratory vane shear test
for the measurement of shear strength of cohesive soils, is useful for soils of low shear strength
(less than 0.3 kg/cm2) for which triaxial or unconfined tests cannot be performed. The test gives
the undrained strength of the soil. The undisturbed and remoulded strength obtained are useful
for evaluating the sensitivity of soil.
PLANNING AND ORGANIZATION
EQUIPMENT
1. Vane shear apparatus.
2. Specimen.
3. Specimen container.
4. Callipers.
EXPERIMENTAL PROCEDURE
1. Prepare two or three specimens of the soil sample of dimensions of at least 37.5 mm diameter
and 75 mm length in specimen.(L/D ratio 2 or 3).
2. Mount the specimen container with the specimen on the base of the vane shear apparatus. If
the specimen container is closed at one end, it should be provided with a hole of about 1 mm
diameter at the bottom.
51
3. Gently lower the shear vanes into the specimen to their full length without disturbing the soil
specimen. The top of the vanes should be at least 10 mm below the top of the specimen. Note the
readings of the angle of twist.
4. Rotate the vanes at an uniform rate say 0.1o/s by suitable operating the torque application
handle until the specimen fails.
5. Note the final reading of the angle of twist.
6. Find the value of blade height in cm.
7. Find the value of blade width in cm.
CALCULATIONS:
Shear strength, S= 𝑇
𝜋(𝐷2𝐻
2+/
𝐷3
6)
52
OBSERVATIONS:
Name of the project:
Soil description:
S.No
Initial
Reading
(Deg)
Final
Reading
(Deg.)
Difference
(Deg.)
T=Spring
Constant/180x
Difference
Kg-cm
G= 1
𝜋(𝐷2𝐻
2+𝐷3
6)
S=TxG
Kg/cm2
Average
'S'
Kg/cm2
Spring
Constant
Kg-cm
GENERAL REMARKS:
This test is useful when the soil is soft and its water content is nearer to liquid lim
53
EXPERIMENT NO. 10 DIRECT SHEAR TEST
OBJECTIVE
To determine the shearing strength of the soil using the direct shear apparatus.
NEED AND SCOPE
In many engineering problems such as design of foundation, retaining walls, slab bridges, pipes,
sheet piling, the value of the angle of internal friction and cohesion of the soil involved are
required for the design. Direct shear test is used to predict these parameters quickly. The
laboratory report covers the laboratory procedures for determining these values for cohesionless
soils.
PLANNING AND ORGANIZATION
Apparatus
1. Direct shear box apparatus
2. Loading frame (motor attached).
3. Dial gauge.
4. Proving ring.
5. Tamper.
6. Straight edge.
7. Balance to weigh up to 200 mg.
8. Aluminum container.
9. Spatula.
KNOWLEDGE OF EQUIPMENT:
Strain controlled direct shear machine consists of shear box, soil container, loading unit, proving
ring, dial gauge to measure shear deformation and volume changes. A two piece square shear
54
box is one type of soil container used. A proving ring is used to indicate the shear load taken by
the soil initiated in the shearing plane.
PROCEDURE
1. Check the inner dimension of the soil container.
2. Put the parts of the soil container together.
3. Calculate the volume of the container. Weigh the container.
4. Place the soil in smooth layers (approximately 10 mm thick). If a dense sample is desired tamp
the soil.
5. Weigh the soil container, the difference of these two is the weight of the soil. Calculate the
density of the soil.
6. Make the surface of the soil plane.
7. Put the upper grating on stone and loading block on top of soil.
8. Measure the thickness of soil specimen.
9. Apply the desired normal load.
10. Remove the shear pin.
11. Attach the dial gauge which measures the change of volume.
12. Record the initial reading of the dial gauge and calibration values.
13. Before proceeding to test check all adjustments to see that there is no connection between
two parts except sand/soil.
14. Start the motor. Take the reading of the shear force and record the reading.
15.Take volume change readings till failure.
16. Add 5 kg normal stress 0.5 kg/cm2 and continue the experiment till failure.
17. Record carefully all the readings. Set the dial gauges zero, before starting the experiment.
55
DATA CALCULATION SHEET FOR DIRECT SHEAR TEST
Normal stress 0.5 kg/cm2
L.C=....... P.R.C=.........
Horizontal
Gauge
Reading
(1)
Vertical
Dial
gauge
Reading
(2)
Proving
ring
Reading
(3)
Hori.Dial
gauge
Reading
Initial
reading
div.
gauge
(4)
Shear
deformation
Col.(4) x
Leastcount of
dial
(5)
Vertical
gauge
reading
Initial
Reading
(6)
Vertical
deformation=
div.in col.6
xL.C of dial
gauge
(7)
Proving
reading
Initial
reading
(8)
Shear stress =
div.col.(8)x
proving ring
constant Area of
the
specimen(kg/cm2)
(9)
0
25
50
75
100
125
150
175
200
250
300
400
500
600
700
800
56
900
Similarly, For Normal stress 1.0 kg/cm2
and Normal stress 1.5 kg/cm2
L.C=....... P.R.C=........
OBSERVATION AND RECORDING
Proving Ring constant....... Least count of the dial........
Calibration factor.......
Leverage factor........
Dimensions of shear box 60 x 60 mm
Empty weight of shear box........
Least count of dial gauge.........
Volume change.......
S.No Normal load (kg)
Normal
stress(kg/cm2) =
load x leverage/Area
Proving ring reading
at failure
Shear stress=
proving Ring
reading x calibration
/ Area of container
1
2
3
57
GENERAL REMARKS
1. In the shear box test, the specimen is not failing along its weakest plane but along a
predetermined or induced failure plane i.e. horizontal plane separating the two halves of
the shear box. This is the main drawback of this test. Moreover, during loading, the state
of stress cannot be evaluated. It can be evaluated only at failure condition i.e. Mohr’s
circle can be drawn at the failure condition only. Also failure is progressive.
2. Direct shear test is simple and faster to operate. As thinner specimens are used in shear
box, they facilitate drainage of pore water from a saturated sample in less time. This test
is also useful to study friction between two materials one material in lower half of box
and another material in the upper half of box.
3. The angle of shearing resistance of sands depends on state of compaction, coarseness of
grains, particle shape and roughness of grain surface and grading. It varies between
28o(uniformly graded sands with round grains in very loose state) to 46
o(well graded sand
with angular grains in dense state).
4. The volume change in sandy soil is a complex phenomenon depending on gradation,
particle shape, state and type of packing, orientation of principal planes, principal stress
ratio, stress history, magnitude of minor principal stress, type of apparatus, test
procedure, method of preparing specimen etc. In general loose sands expand and dense
sands contract in volume on shearing. There is a void ratio at which either expansion
contraction in volume takes place. This void ratio is called critical void ratio. Expansion
or contraction can be inferred from the movement of vertical dial gauge during shearing.
5. The friction between sand particles is due to sliding and rolling friction and interlocking
action.
The ultimate values of shear parameter for both loose sand and dense sand approximately attain the same
value so, if angle of friction value is calculated at ultimate stage, slight disturbance in density during
sampling and preparation of test specimens will not have much effect.
58
EXPERIMENT NO. 11
UNCONFINED COMPRESSION TEST
OBJECTIVE
Determine Shear Parameters of Cohesive Soil
NEED AND SCOPE OF THE EXPERIMENT
It is not always possible to conduct the bearing capacity test in the field. Sometimes it is cheaper
to take the undisturbed soil sample and test its strength in the laboratory. Also to choose the best
material for the embankment, one has to conduct strength tests on the samples selected. Under
these conditions it is easy to perform the unconfined compression test on undisturbed and
remolded soil sample. Now we will investigate experimentally the strength of a given soil
sample.
PLANNING AND ORGANIZATION
We have to find out the diameter and length of the specimen.
EQUIPMENT
1. Loading frame of capacity of 2 t, with constant rate of movement. What is the least count
of the dial gauge attached to the proving ring!
2. Proving ring of 0.01 kg sensitivity for soft soils; 0.05 kg for stiff soils.
3. Soil trimmer.
4. Frictionless end plates of 75 mm diameter (Perspex plate with silicon grease coating).
5. Evaporating dish (Aluminum container).
6. Soil sample of 75 mm length.
7. Dial gauge (0.01 mm accuracy).
8. Balance of capacity 200 g and sensitivity to weigh 0.01 g.
9. Oven thermostatically controlled with interior of non-corroding material to maintain the
temperature at the desired level. What is the range of the temperature used for drying the
soil!
59
10. Sample extractor and split sampler.
11. Dial gauge (sensitivity 0.01mm).
12. Vernier calipers
EXPERIMENTAL PROCEDURE (SPECIMEN)
In this test, a cylinder of soil without lateral support is tested to failure in simple compression, at
a constant rate of strain. The compressive load per unit area required to fail the specimen as
called unconfined compressive strength of the soil.
Preparation of specimen for testing
Undisturbed specimen
a. Note down the sample number, bore hole number and the depth at which the
sample was taken. b. Remove the protective cover (paraffin wax) from the sampling tube. c. Place the sampling tube extractor and push the plunger till a small length of
sample moves out. d. Trim the projected sample using a wire saw. e. Again push the plunger of the extractor till a 75 mm long sample comes out. f. Cutout this sample carefully and hold it on the split sampler so that it does not
fall. g. Take about 10 to 15 g of soil from the tube for water content determination. h. Note the container number and take the net weight of the sample and the
container. i. Measure the diameter at the top, middle, and the bottom of the sample and find
the average and record the same. j. Measure the length of the sample and record. k. Find the weight of the sample and record.
60
Moulded sample
1. For the desired water content and the dry density, calculate the weight of the dry soil
Ws required for preparing a specimen of 3.8 cm diameter and 7.5 cm long. 2. Add required quantity of water Ww to this soil.
i. Ww = WS ×W/100 gm
3. Mix the soil thoroughly with water. 4. Place the wet soil in a tight thick polythene bag in a humidity chamber and place the
soil in a constant volume mould, having an internal height of 7.5 cm and internal
diameter of 3.8 cm. 5. After 24 hours take the soil from the humidity chamber and place the soil in a
constant volume mould, having an internal height of 7.5 cm and internal diameter of
3.8 cm. 6. Place the lubricated moulded with plungers in position in the load frame. 7. Apply the compressive load till the specimen is compacted to a height of 7.5 cm. 8. Eject the specimen from the constant volume mould. 9. Record the correct height, weight and diameter of the specimen.
TEST PROCEDURE
1. Take two frictionless bearing plates of 75 mm diameter.
2. Place the specimen on the base plate of the load frame (sandwiched between the
end plates).
3. Place a hardened steel ball on the bearing plate.
4. Adjust the center line of the specimen such that the proving ring and the steel ball
are in the same line.
5. Fix a dial gauge to measure the vertical compression of the specimen.
6. Adjust the gear position on the load frame to give suitable vertical displacement.
7. Start applying the load and record the readings of the proving ring dial and
compression dial for every 5 mm compression.
8. Continue loading till failure is complete.
9. Draw the sketch of the failure pattern in the specimen.
61
Project : Tested by :
Location : Boring No. :
Depth :
Sample details
Type UD/R : soil description
Specific gravity (GS)…….. Bulk density …………
Water content……. Degree of saturation……. ...%
Diameter (Do) of the sample =…….. cm Area of cross-section =……. cm2
Initial length (Lo) of the sample = 76 mm
Elapsed time
(minutes)
1
Compression
dial
reading (L)
(mm)
2
Strain
L × 100/Lo
(%) (e)
3
Area A ,
Ao /(1-e)
(cm)2
4
Proving ring
reading
(Divns.)
5
Axial
load
(kg)
6
Compressive
stress
(kg/cm2)
7
Interpretation and Reporting
Unconfined compression strength of the soil = qu =
Shear strength of the soil = qu/2 =
Sensitivity = (qu for undisturbed sample)/ (qu for remoulded sample).
62
General Remarks
Minimum three samples should be tested; correlation can be made between unconfined strength
and field SPT value N. Up to 6% strain the readings may be taken at every min (30 sec).
63
EXPERIMENT NO. 12
UNDRAINED TRIAXIAL TEST
OBJECTIVE
To find the shear of the soil by Undrained Triaxial Test.
NEED AND SCOPE OF THE TEST
The standard consolidated undrained test is compression test, in which the soil specimen is first
consolidated under all round pressure in the triaxial cell before failure is brought about by
increasing the major principal stress.
It may be perform with or without measurement of pore pressure although for most applications
the measurement of pore pressure is desirable.
PLANNING AND ORGANIZATION
Knowledge of Equipment
A constant rate of strain compression machine of which the following is a brief description of one is
in common use.
a) A loading frame in which the load is applied by a yoke acting through an elastic dynamometer,
more commonly called a proving ring which used to measure the load. The frame is operated at a
constant rate by a geared screw jack. It is preferable for the machine to be motor driven, by a
small electric motor.
b) A hydraulic pressure apparatus including an air compressor and water reservoir in which air
under pressure acting on the water raises it to the required pressure, together with the necessary
control valves and pressure dials.
A triaxial cell to take 3.8 cm dia and 7.6 cm long samples, in which the sample can be
subjected to an all round hydrostatic pressure, together with a vertical compression load acting
64
through a piston. The vertical load from the piston acts on a pressure cap. The cell is usually
designed with a non-ferrous metal top and base connected by tension rods and with walls formed
of Perspex.
Apparatus for preparation of the sample :
a) 3.8 cm (1.5 inch) internal diameter 12.5 cm (5 inches) long sample tubes.
b) Rubber ring.
c) An open ended cylindrical section former, 3.8 cm inside dia, fitted with a small rubber
tube in its side.
d) Stop clock.
e) Moisture content test apparatus.
f) A balance of 250 gm capacity and accurate to 0.01 gm.
Experimental Procedure
1. The sample is placed in the compression machine and a pressure plate is placed
on the top. Care must be taken to prevent any part of the machine or cell from
jogging the sample while it is being setup, for example, by knocking against this
bottom of the loading piston. The probable strength of the sample is estimated and
a suitable proving ring selected and fitted to the machine.
2. The cell must be properly set up and uniformly clamped down to prevent
leakage of pressure during the test, making sure first that the sample is properly
sealed with its end caps and rings (rubber) in position and that the sealing rings
for the cell are also correctly placed.
3. When the sample is setup water is admitted and the cell is fitted under water
escapes from the beed valve, at the top, which is closed. If the sample is to be
tested at zero lateral pressure water is not required.
4. The air pressure in the reservoir is then increased to raise the hydrostatic
pressure in the required amount. The pressure gauge must be watched during the
test and any necessary adjustments must be made to keep the pressure constant.
65
5. The handle wheel of the screw jack is rotated until the underside of the
hemispherical seating of the proving ring, through which the loading is applied,
just touches the cell piston.
6. The piston is then removed down by handle until it is just in touch with the
pressure plate on the top of the sample, and the proving ring seating is again
brought into contact for the begging of the test.
Observation and Recording
The machine is set in motion (or if hand operated the hand wheel is turned at a constant rate) to
give a rate of strain 2% per minute. The strain dial gauge reading is then taken and the
corresponding proving ring reading is taken the corresponding proving ring chart. The load
applied is known. The experiment is stopped at the strain dial gauge reading for 15% length of
the sample or 15% strain.
Operator : Sample No:
Date : Job :
Location : Size of specimen :
Length : Proving ring constant :
Diameter : 3.81 cm Initial area L:
Initial Volume : Strain dial least count (const) :
66
Cell pressure
kg/cm2
1
Strain dial
2
Proving ring
reading
3
Load on sample
kg
4
Corrected area
cm2
5
Deviator stress
6
0.5
0
50
100
150
200
250
300
350
400
450
0.5
0
50
100
150
200
250
300
350
400
450
0.5 0
67
50
100
150
200
250
300
350
400
450
Sample
No.
Wet bulk
density gm/cc
Cell pressure
kg/cm2
Compressive
stress
at failure
Strain at
failure
Moisture
content
Shear
strength
(kg/cm2)
Angle of
shearing
resistance
1.
2.
3.
General Remarks
a) It is assumed that the volume of the sample remains constant and that the area of the
sample increases uniformly as the length decreases. The calculation of the stress is based
on this new area at failure, by direct calculation, using the proving ring constant and the
new area of the sample. By constructing a chart relating strain readings, from the proving
ring, directly to the corresponding stress.
68
b) The strain and corresponding stress is plotted with stress abscissa and curve is drawn.
The maximum compressive stress at failure and the corresponding strain and cell pressure
are found out.
c) The stress results of the series of triaxial tests at increasing cell pressure are plotted on a
Mohr stress diagram. In this diagram a semicircle is plotted with normal stress as abscissa
shear stress as ordinate.
d) The condition of the failure of the sample is generally approximated to by a straight line
drawn as a tangent to the circles, the equation of which is = C + tan. The value of cohesion
is read of the shear stress axis, where it is cut by the tangent to the Mohr circles, and the angle of
shearing resistance () is angle between the tangent and a line parallel to the shear stress.
69
EXPERIMENT NO. 13
CONSOLIDATION TEST
OBJECTIVE
To determine the settlements due to primary consolidation of soil by conducting one dimensional
test.
NEED AND SCOPE
The test is conducted to determine the settlement due to primary consolidation. To determine :
i. Rate of consolidation under normal load.
ii. Degree of consolidation at any time.
iii. Pressure-void ratio relationship.
iv. Coefficient of consolidation at various pressures.
v. Compression index.
From the above information it will be possible for us to predict the time rate and extent of
settlement of structures founded on fine-grained soils. It is also helpful in analyzing the stress
history of soil. Since the settlement analysis of the foundation depends mainly on the values
determined by the test, this test is very important for foundation design.
PLANNING AND ORGANIZATION
1. Consolidometer consisting essentially
a) A ring of diameter = 60mm and height = 20mm
b) Two porous plates or stones of silicon carbide, aluminum oxide or porous metal.
c) Guide ring.
d) Outer ring.
e) Water jacket with base.
f) Pressure pad.
g) Rubber basket.
70
2. Loading device consisting of frame, lever system, loading yoke dial gauge fixing device
and weights.
3. Dial gauge to read to an accuracy of 0.002mm.
4. Thermostatically controlled oven.
5. Stopwatch to read seconds.
6. Sample extractor.
7. Miscellaneous items like balance, soil trimming tools, spatula, filter papers, sample
containers.
PRINCIPAL INVOLVED
When a compressive load is applied to soil mass, a decrease in its volume takes place, the
decease in volume of soil mass under stress is known as compression and the property of soil
mass pertaining to its tendency to decrease in volume under pressure is known as
compressibility. In a saturated soil mass having its void filled with incompressible water,
decrease in volume or compression can take place when water is expelled out of the voids. Such
a compression resulting from a long time static load and the consequent escape of pore water is
termed as consolidation.
Then the load is applied on the saturated soil mass, the entire load is carried by pore water in the
beginning. As the water starts escaping from the voids, the hydrostatic pressure in water gets
gradually dissipated and the load is shifted to the soil solids which increases effective on them,
as a result the soil mass decrease in volume. The rate of escape of water depends on the
permeability of the soil.
1) From the sample tube, eject the sample into the consolidation ring. The sample should
project about one cm from outer ring. Trim the sample smooth and flush with top and bottom
of the ring by using a knife. Clean the ring from outside and keep it ready from weighing.
2) Remolded sample:
a) Choose the density and water content at which samples have to be compacted from the
moisture density relationship.
71
b) Calculate the quantity of soil and water required to mix and compact.
c) Compact the specimen in compaction mould in three layers using the standard
rammers.
d) Eject the specimen from the mould using the sample extractor.
PROCEDURE
1. Saturate two porous stones either by boiling in distilled water about 15 minute or by
keeping them submerged in the distilled water for 4 to 8 hrs. Wipe away excess water.
Fittings of the consolidometer which is to be enclosed shall be moistened.
2. Assemble the consolidometer, with the soil specimen and porous stones at top and bottom
of specimen, providing a filter paper between the soil specimen and porous stone.
Position the pressure pad centrally on the top porous stone.
3. Mount the mould assembly on the loading frame, and center it such that the load applied
is axial.
4. Position the dial gauge to measure the vertical compression of the specimen. The dial
gauge holder should be set so that the dial gauge is in the begging of its releases run,
allowing sufficient margin for the swelling of the soil, if any.
5. Connect the mould assembly to the water reservoir and the sample is allowed to saturate.
The level of the water in the reservoir should be at about the same level as the soil
specimen.
6. Apply an initial load to the assembly. The magnitude of this load should be chosen by
trial, such that there is no swelling. It should be not less than 50 g/cm3 for ordinary soils
& 25 g/cm2 for very soft soils. The load should be allowed to stand until there is no
change in dial gauge readings for two consecutive hours or for a maximum of 24 hours.
7. Note the final dial reading under the initial load. Apply first load of intensity 0.1 kg/cm2
start the stop watch simultaneously. Record the dial gauge readings at various time
intervals. The dial gauge readings are taken until 90% consolidation is reached. Primary
consolidation is gradually reached within 24 hrs.
72
8. At the end of the period, specified above take the dial reading and time reading. Double
the load intensity and take the dial readings at various time intervals. Repeat this
procedure fir successive load increments. The usual loading intensity are as follows :
a. 0.1, 0.2, 0.5, 1, 2, 4 and 8 kg/cm2.
9. After the last loading is completed, reduce the load to of the value of the last load and
allow it to stand for 24 hrs. Reduce the load further in steps of the previous intensity till
an intensity of 0.1 kg/cm2 is reached. Take the final reading of the dial gauge.
10. Reduce the load to the initial load, keep it for 24 hrs and note the final readings of the dial
gauge.
11. Quickly dismantle the specimen assembly and remove the excess water on the soil
specimen in oven, note the dry weight of it.
OBSERVATION AND READING
Table
Data and observation sheet for consolidation test pressure, compression and time.
Project: Name of the project Borehole no. : 1
Depth of the sample: 2m Description of soil:
Empty weight of ring: 635 gm Area of ring: 4560 mm2 (45.60 cm
2)
Diameter of ring: 76.2 mm (7.62 cm) Volume of ring: 115.82 cm3
Height of ring: 25.4 (2.54 cm) Specific gravity of soil sample No:
Dial Gauge = 0.0127 mm (least count)
73
Pressure
Intensity
(Kg/cm2)
0.1 0.2 0.5 1 2 4 8
Elapsed Time
0.25
1
2.5
4
6.25
9
16
25
30
1 hr
2 hrs
4 hrs
8 hrs
24 hrs
74
Observation Sheet for Consolidation Test:
Pressure Voids Ratio
Applied
pressure
Final dial
reading Dial change
Specimen
height Height solids
Height of
voids Void ration
0
0.1
0.2
0.5
1.0
2.0
4.0
8.0
4.0
2.0
1.0
0.5
0.2
0.1
CALCULATIONS
1. Height of solids (HS) is calculated from the equation
HS = WSd/GA
2. Void ratio. Voids ratio at the end of various pressures are calculated from equation
75
e = (H - HS)/HS
3. Coefficient of consolidation. The Coefficient of consolidation at each pressures increment is
calculated by using the following equations:
i. Cv = 0.197 d2/t50 (Log fitting method)
ii. Cv = 0.848 d2/t90 (Square fitting method)
In the log fitting method, a plot is made between dial readings and logarithmic of time, the time
corresponding to 50% consolidation is determined.
In the square root fitting method, a plot is made between dial readings and square root of time
and the time corresponding to 90% consolidation is determined. The values of Cv are recorded in
table.
4. Compression Index. To determine the compression index, a plot of voids ratio (e) Vs logt is
made. The initial compression curve would be a straight line and the slope of this line would give
the compression index Cc.
5. Coefficient of compressibility. It is calculated as follows
av = 0.435 Cc/Avg. pressure for the increment
where Cc = Coefficient of compressibility
6. Coefficient of permeability. It is calculated as follows
K = Cv.av *(unit weight of water)/(1+e).
Graphs
1. Dial reading VS log of time or Dial reading VS square root of time.
2. Voids ratio VS logˡ (average pressure for the increment).
76
General Remarks
1. While preparing the specimen, attempts has to be made to have the soil strata orientated in the
same direction in the consolidation apparatus.
2. During trimming care should be taken in handling the soil specimen with least pressure.
3. Smaller increments of sequential loading have to be adopted for soft soils.
77
EXPERIMENT NO. 14
CBR TEST
OBJECTIVE
To determine the C.B.R value of given soil sample.
THEORY
The California bearing ratio test is penetration test meant for the evaluation of sub grade strength
of roads and pavements. The results obtained by these tests are used with the empirical curves to
determine the thickness of pavement and its component layers. This is the most widely used
method for the design of flexible pavement. This Chapter covers the laboratory method for the
determination of C.B.R. of undisturbed and remolded /compacted soil specimens, both in soaked
as well as unsoaked state.
Equipments and tool required:-
1. Cylindrical mould with inside dia 150 mm and height 175 mm, provided with a detachable
extension collar 50 mm height and a detachable perforated base plate 10 mm thick.
2. Spacer disc 148 mm in dia and 47.7 mm in height along with handle.
3. Metal rammers. Weight 2.6 kg with a drop of 310 mm (or) weight 4.89 kg a drop 450 mm.
4. Weights. One annular metal weight and several slotted weights weighing 2.5 kg each,
147 mm in dia, with a central whole 53 mm in diameter.
5. Loading machine. With a capacity of atleast 5000 kg and equipped with a movable head or
base that travels at an uniform rate of 1.25 mm/min. Complete with load indicating device.
6. Metal penetration piston 50 mm dia and minimum of 100 mm in length.
7. Two dial gauges reading to 0.01 mm.
8. Sieves. 4.75 mm and 20 mm I.S. Sieves.
9. Miscellaneous apparatus, such as a mixing bowl, straight edge, scales soaking tank or pan, drying
oven, filter paper and containers.
78
Fig. California Bearing Ratio (CBR) Testing machine &equipments
Definition of C.B.R.
It is the ratio of force per unit area required to penetrate a soil mass with standard circular piston at
the rate of 1.25 mm/min. to that required for the corresponding penetration of a standard material.
C.B.R. = (Test load/Standard load) X 100
The following table gives the standard loads adopted for different penetrations for the standard
material with a C.B.R. value of 100%
Table: Standard loads for different penetrations
Penetration (mm) Load(Kg)
2.5 1370
5 2055
7.5 2630
10 3180
12.5 3600
79
The test may be performed on undisturbed specimens and on remolded specimens which may be
compacted either statically or dynamically.
Preparation of Test Specimen
Undisturbed specimen: Attach the cutting edge to the mould and push it gently into the
ground. Remove the soil from the outside of the mould which is pushed in. When the
mould is full of soil, remove it from weighing the soil with the mould or by any field
method near the spot. Determine the density
Remolded specimen: Prepare the remolded specimen at Proctors maximum dry density
or any other density at which C.B.R> is required. Maintain the specimen at optimum
moisture content or the field moisture as required. The material used should pass 20 mm
I.S. sieve but it should be retained on 4.75 mm.
3.5.1 Dynamic Compaction
Take about 4.5 to 5.5 kg of soil and mix thoroughly with the required water. Fix the
extension collar and the base plate to the mould. Insert the spacer disc over the base.
Place the filter paper on the top of the spacer disc.
Compact the mix soil in the mould using either light compaction or heavy compaction.
For light compaction, compact the soil in 3 equal layers, each layer being given 55 blows
by the 2.6 kg rammer. For heavy compaction compact the soil in 5 layers, 56 blows to
each layer by the 4.89 kg rammer.
Remove the collar and trim off soil.
Turn the mould upside down and remove the base plate and the displacer disc.
Weigh the mould with compacted soil and determine the bulk density and dry density.
Put filter paper on the top of the compacted soil (collar side) and clamp the perforated
base plate on to it.
80
Static Compaction
Calculate the weight of the wet soil at the required water content to give the desired density
when occupying the standard specimen volume in the mould from the expression.
W =desired dry density × (1+w) V
Where W = Weight of the wet soil
w = desired water content
V = volume of the specimen in the mould
Take the weight W (calculated as above) of the mix soil and place it in the mould.
Place a filter paper and the displacer disc on the top of soil.
Keep the mould assembly in static loading frame and compact by pressing the displacer
disc till the level of disc reaches the top of the mould.
Keep the load for some time and then release the load. Remove the displacer disc.
The test may be conducted for both soaked as well as unsoaked conditions.
If the sample is to be soaked, in cases of compaction, put a filter paper on the top of the
soil and place the adjustable stem and perforated plate on the top of filter paper.
Put annular weights to produce a surcharge equal to weight of base material and
pavement expected in actual construction. Each 2.5 kg weight is equva-lent to 7 cm
construction. A minimum of two weights should be put.
Immerse the mould assembly and weights in a tank of water and soak it for 96 hours.
Remove the mould from tank.
Note the consolidation of the specimen
Procedure for Penetration Test
Place the mould assembly with the surcharge weights on the penetration test machine.
Seat the penetration piston at the center of the specimen with the smallest possible load,
but in no case in excess of 4 kg so that full contact of the piston on the sample is
established.
81
Set the stress and strain dial gauge to read zero. Apply the load on the piston so that the
penetration rate is about 1.25 mm/min.
Record the load readings at penetrations of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0,
7.5, 10 and 12.5 mm. Note the maximum load and corresponding penetration if it occurs
for a penetration less than 12.5 mm.
Detach the mould from the loading equipment. Taken about 20 to 50 g of soil from the
top 3 cm layer and determine the moisture content.
Observation and Recording
For Dynamic Compaction
Optimum water content (%)
Weight of mould + compacted specimen (gm)
Weight of empty mould gm
Weight of compacted specimen (gm)
Volume of specimen cm3
Bulk density g/cc
Dry density g/cc
For static compaction
Dry density g/cc
Moulding water content %
Wet weight of the compacted soil, (W)gm
Period of soaking 96 hrs. (4days).
If the initial portion of the curve is concave upwards, apply correction by drawing a
tangent to the curve at the point of greatest slope and shift the origin. Find and record the
correct load reading corresponding to each penetration.
Interpretation and recording
C.B.R. of specimen at 2.5 mm penetration
82
C.B.R. of specimen at 5.0 mm penetration
The C.B.R. values are usually calculated for penetration of 2.5 mm and 5 mm. Generally the
C.B.R. value at 2.5 mm will be greater that at 5 mm and in such a case/the former shall be taken
as C.B.R. for design purpose. If C.B.R. for 5 mm exceeds that for 2.5 mm, the test should be
repeated. If identical results follow, the C.B.R. corresponding to 5 mm penetration should be
taken for design.
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